implement direct TLLI in immediate assignments over AGCH

Ericsson allows to attach a reference to immediate assignments. A
confirmation of the transmission is then sent back, but only containing
the reference, not the whole RLC packet.

Change-Id: I000984d92de2017bf2d1619b42a75e6f28388f87

6 files changed, 37 insertions, 3 deletions

diff --git a/include/osmocom/pcu/pcuif_proto.h b/include/osmocom/pcu/pcuif_proto.h
index f6e167af..f29e2b6e 100644
--- a/include/osmocom/pcu/pcuif_proto.h
+++ b/include/osmocom/pcu/pcuif_proto.h
@@ -3,7 +3,7 @@
 
 #include <osmocom/gsm/l1sap.h>
 
-#define PCU_IF_VERSION		0x07
+#define PCU_IF_VERSION		0x08
 
 /* msg_type */
 #define PCU_IF_MSG_DATA_REQ	0x00	/* send data to given channel */
@@ -25,6 +25,7 @@
 #define PCU_IF_SAPI_PDTCH	0x05	/* packet data/control/ccch block */
 #define PCU_IF_SAPI_PRACH	0x06	/* packet random access channel */
 #define PCU_IF_SAPI_PTCCH	0x07	/* packet TA control channel */
+#define PCU_IF_SAPI_AGCH_DT	0x08	/* assignment on AGCH but with additional TLLI */
 
 /* flags */
 #define PCU_IF_FLAG_ACTIVE	(1 << 0)/* BTS is active */
diff --git a/src/bts.cpp b/src/bts.cpp
index 8e60a571..773b7a13 100644
--- a/src/bts.cpp
+++ b/src/bts.cpp
@@ -647,7 +647,10 @@ int BTS::rcv_rach(uint16_t ra, uint32_t Fn, int16_t qta, uint8_t is_11bit,
 
 	if (plen >= 0) {
 		immediate_assignment_ul_tbf();
-		pcu_l1if_tx_agch(immediate_assignment, plen);
+		if (this->bts_data()->use_direct_tlli)
+			pcu_l1if_tx_agch_dt(tbf->tlli(), immediate_assignment, plen);
+		else
+			pcu_l1if_tx_agch(immediate_assignment, plen);
 	}
 
 	bitvec_free(immediate_assignment);
@@ -778,7 +781,10 @@ void BTS::snd_dl_ass(gprs_rlcmac_tbf *tbf, uint8_t poll, const char *imsi)
 		tbf->poll_fn, m_bts.alpha, m_bts.gamma, -1);
 	if (plen >= 0) {
 		immediate_assignment_dl_tbf();
-		pcu_l1if_tx_agch(immediate_assignment, plen);
+		if (this->bts_data()->use_direct_tlli)
+			pcu_l1if_tx_agch_dt(tbf->tlli(), immediate_assignment, plen);
+		else
+			pcu_l1if_tx_agch(immediate_assignment, plen);
 	}
 
 	bitvec_free(immediate_assignment);
diff --git a/src/bts.h b/src/bts.h
index e8118dd6..1074bc22 100644
--- a/src/bts.h
+++ b/src/bts.h
@@ -158,6 +158,7 @@ void bts_update_tbf_ta(const char *p, uint32_t fn, uint8_t trx_no, uint8_t ts,
  */
 struct gprs_rlcmac_bts {
 	uint8_t bsic;
+	uint8_t use_direct_tlli;
 	uint8_t fc_interval;
 	uint16_t fc_bucket_time;
 	uint32_t fc_bvc_bucket_size;
diff --git a/src/pcu_l1_if.cpp b/src/pcu_l1_if.cpp
index a72c6b2c..1c5aa4b7 100644
--- a/src/pcu_l1_if.cpp
+++ b/src/pcu_l1_if.cpp
@@ -172,6 +172,17 @@ void pcu_l1if_tx_agch(bitvec * block, int plen)
 	pcu_tx_data_req(0, 0, PCU_IF_SAPI_AGCH, 0, 0, 0, data, sizeof(data));
 }
 
+void pcu_l1if_tx_agch_dt(uint32_t tlli, bitvec * block, int plen)
+{
+	uint8_t data[27]; /* prefix tlli and PLEN */
+	memcpy(data, &tlli, sizeof(uint32_t));
+
+	/* FIXME: why does OpenBTS has no PLEN and no fill in message? */
+	bitvec_pack(block, data + 5);
+	data[4] = (plen << 2) | 0x01;
+	pcu_tx_data_req(0, 0, PCU_IF_SAPI_AGCH_DT, 0, 0, 0, data, sizeof(data));
+}
+
 void pcu_l1if_tx_pch(bitvec * block, int plen, const char *imsi)
 {
 	uint8_t data[23+3]; /* prefix PLEN */
diff --git a/src/pcu_l1_if.h b/src/pcu_l1_if.h
index d9d970da..0826075f 100644
--- a/src/pcu_l1_if.h
+++ b/src/pcu_l1_if.h
@@ -120,6 +120,8 @@ void pcu_l1if_tx_pdtch(msgb *msg, uint8_t trx, uint8_t ts, uint16_t arfcn,
 void pcu_l1if_tx_ptcch(msgb *msg, uint8_t trx, uint8_t ts, uint16_t arfcn, 
         uint32_t fn, uint8_t block_nr);
 void pcu_l1if_tx_agch(bitvec * block, int len);
+/* same as agch but has tlli prefixed */
+void pcu_l1if_tx_agch_dt(uint32_t tlli, bitvec * block, int len);
 
 void pcu_l1if_tx_pch(bitvec * block, int plen, const char *imsi);
 
diff --git a/src/pcu_vty.c b/src/pcu_vty.c
index 535d512b..fa250d88 100644
--- a/src/pcu_vty.c
+++ b/src/pcu_vty.c
@@ -741,6 +741,18 @@ DEFUN(show_bts_stats,
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_pcu_use_direct_tlli,
+      cfg_pcu_use_direct_tlli_cmd,
+      "use-direct-tlli <0-1>",
+      "use direct tlli message when sending AGCH message.\n")
+{
+	struct gprs_rlcmac_bts *bts = bts_main_data();
+
+	bts->use_direct_tlli = atoi(argv[0]);
+
+	return CMD_SUCCESS;
+}
+
 #define IDLE_TIME_STR "keep an idle DL TBF alive for the time given\n"
 DEFUN(cfg_pcu_dl_tbf_idle_time,
       cfg_pcu_dl_tbf_idle_time_cmd,
@@ -958,6 +970,7 @@ int pcu_vty_init(const struct log_info *cat)
 	install_node(&pcu_node, config_write_pcu);
 	install_element(CONFIG_NODE, &cfg_pcu_cmd);
 	vty_install_default(PCU_NODE);
+	install_element(PCU_NODE, &cfg_pcu_use_direct_tlli_cmd);
 	install_element(PCU_NODE, &cfg_pcu_egprs_cmd);
 	install_element(PCU_NODE, &cfg_pcu_no_egprs_cmd);
 	install_element(PCU_NODE, &cfg_pcu_no_two_phase_cmd);